The invention is generally related to methods of obtaining pharmacologically active extracts of the cell walls of Gram-positive bacteria. More particularly these extracts have immune stimulating and anti-tumor activities with no toxicity at effective doses. The final products are stable, water-soluble powders.
Bacterial and fungal cell wall extracts have previously been used as immune stimulants and anti-tumor agents, examples are Bacillus Calmette-Guerin (BCG), Polysaccharide K, beta 1,3, glucan, the Maruyama vaccine, and extracts of Bifidobacterium, L. lactis, L. fermentum, L. acidophilus and, S. lactis. 
Such extracts are thought to stimulate the immune system in a number of ways. One important way is to stimulate lymphocytes, well known to be involved in anti-tumor reactions in humans and animals, to grow and to produce cytokines. The cytokines produced by the lymphocytes then stimulate the immune system. For example, the cytokine interleukin-6 (IL-6) is a potent lymphoid cell growth factor that acts on B lymphocytes, and T lymphocytes. IL-6 will also act on cytotoxic T-cells in combination with other factors such as interleukin-2 (IL-2) and interferon-gamma. The cytokine interleukin-12 (IL-12) induces interferon-gamma production, enhances cytotoxic T cell responses, increases natural killer cell activity, has dramatic anti-tumor properties in a number of murine tumor models, induces regression of many established tumors, and decreases pulmonary and hepatic metastases. Therefore, the ability to induce production of such cytokines has a very powerful effect on the immune system.
All bacteria containing a cell wall, and particularly Gram positive bacteria, possess a specific component of the cell wall called peptidoglycan. The peptidoglycan provides structural support to the bacterial cell. A very early finding in the field of microbiology was that there was considerably more peptidoglycan in the Gram positive cell wall then in the Gram negative cell wall of bacteria, causing the differential Gram staining of such bacteria. The ability of the peptidoglycan to activate an immune response or act as an anti-tumor agent was a later finding in the field. Peptidoglycan is made up of alternating sugar units (N-acetylglucosamine and N-acetylmuramic acid). The sugars are joined by short peptide chains that consist of four amino acids. The sugars and tetrapeptides are crosslinked by a simple peptide bond. It is believed that the muramic acid and muramopeptides have nonspecific immunostimulatory properties, however, the exact mechanism of immunostimulation is still not clear.
U.S. Pat. No. 5,601,999 discloses an extract containing bacterial peptidoglycan which was specifically treated with a cell wall lytic enzyme. The enzyme Achromopeptidase attacks the peptidoglycan at the N-acetylmuramic acid linkages. When the extract produced with this enzyme was injected into mice with subcutaneous fibrosarcomas, the peptidoglycan extract showed a significant antitumor effect. Of course, the mechanism of the anti-tumor effect was not clear. In addition, such an extract is extremely expensive to prepare because of the treatment of peptidoglycan with the specific Achromopeptidase enzyme from Achromobacter. 
Of interest is a peptidoglycan extract which has comparable anti-tumor effects, but is easier and less expensive to produce.